Conventionally, an ejector-type refrigerant cycle device having an ejector, provided with functions of a refrigerant decompression means and a refrigerant circulating means, is known, for example, in Patent Documents 1 to 3 (JP Patent No. 3322263 (corresponding to US 2001/0025499A1), JP Patent No. 3931899 (corresponding to US 2005/0178150A1), JP 2008-107055A (corresponding to US 2008/0098757A1)).
In the ejector adopted to the above ejector-type refrigerant cycle device, refrigerant is decompressed and expanded in a nozzle portion of the ejector in iso-entropy, and the refrigerant downstream of a suction side evaporator is drawn into the ejector from a refrigerant suction port by refrigerant suction action due to a high-speed refrigerant jetted from a jet port of the nozzle portion, thereby recovering the loss of the kinetic energy caused in the decompression and expansion of the nozzle portion.
Furthermore, the recovered kinetic energy is converted to the pressure energy in a diffuser portion (pressure increasing portion) of the ejector, thereby increasing the pressure of the refrigerant to be drawn into the compressor. Thus, the drive power of the compressor is reduced, thereby improving the coefficient of performance (COP).
It is desired to reduce unnecessary energy consumption in a driving device for driving a compressor while improving the COP in a refrigerant cycle device including an ejector-type refrigerant cycle device. For example, in a compressor driven by an engine, it is desired to reduce a fuel consumption in the engine.
In order to reduce the fuel consumption, Patent Document 4 (JP 2006-272982A) describes regarding a torque estimating device, which estimates a drive torque of a compressor for a refrigerant cycle. An energy amount supplied to a driving device is controlled based on the estimated drive torque, thereby reducing the fuel consumption.
More specifically, in JP Patent Document 4, the torque estimating device is adapted to a refrigerant cycle device that includes the compressor driven by the engine, a radiator for cooling the refrigerant discharged from the compressor, an expansion device for decompressing and expanding the refrigerant flowing out of the radiator, and an evaporator for evaporating the refrigerant decompressed and expanded in the expansion device.
The drive torque of the compressor is estimated by using a pressure increasing amount of the compressor and a refrigerant discharge amount of the compressor. Here, the pressure increasing amount of the compressor is a difference value between a discharge refrigerant pressure and a suction refrigerant pressure in the compressor, and the refrigerant discharge amount corresponds to a circulation refrigerant flow amount circulating in a refrigerant cycle.
In Patent Document 4, more specifically, a pressure difference between the pressure of a high-pressure side refrigerant from a discharge port of the compressor to a refrigerant inlet side of the expansion device, and the pressure of a low-pressure side refrigerant from a refrigerant outlet side of the expansion device to the suction side of the compressor, is adopted as the pressure increasing amount of the compressor, and the circulation refrigerant discharge amount is calculated based on the rotation speed of the compressor, so as to estimate the drive torque of the compressor.
In the Patent Document 4, the pressure of the low-pressure side refrigerant is calculated from a refrigerant evaporation temperature.
On the other hand, in the ejector-type refrigerant cycle device, the refrigerant flowing out of a suction side evaporator is drawn into a refrigerant suction port of the ejector, and the refrigerant pressurized in the diffuser portion of the ejector is drawn into the compressor.
Therefore, the refrigerant evaporation pressure of the suction side evaporator is different from the refrigerant pressure drawn into the compressor in the ejector-type refrigerant cycle device. Thus, even when the torque estimating device of the Patent Document 4 is used for the ejector-type refrigerant cycle device described in the Patent Documents 1 to 3, it is difficult to accurately estimate the drive torque of the compressor.